Now let's take apart the code of some of our previous example programs.

The following appeared in the simple examples chapter.

def fact(n)
  if n == 0
    1
  else
    n * fact(n-1)
  end
end
print fact(ARGV[0].to_i), "\n"

Because this is …

You can create an array by listing some items within square brackets ([]) and separating them with commas. Ruby's arrays can accomodate diverse object types.

ruby> ary = [1, 2, "3"]
   [1, 2, "3"]

Arrays can be concatenated or repeated …

Let's put together a more interesting program. This time we test whether a string fits a description, encoded into a concise pattern .

There are some characters and character combinations that have special meaning in these patterns, including:

[] - …

Ruby deals with strings as well as numerical data. A string may be double-quoted ("...") or single-quoted ('...').

ruby> "abc"
   "abc"
ruby> 'abc'
   "abc"

Double- and single-quoting have different effects in some cases. A double-quoted string allows character escapes by …

Let's write a function to compute factorials. The mathematical definition of n factorial is:

n! = 1                (when n==0)
   = n * (n-1)!       (otherwise)

In ruby, this can be written as:

def fact(n)
  if n == 0
    1
  else
    n …

First, you'll want to check whether ruby is installed. From the shell prompt (denoted here by "

%

%

% ruby -v

( -v tells the interpreter to print the version of ruby), …

Ruby is "an interpreted scripting language for quick and easy object-oriented programming"; what does this mean?

interpreted scripting language:

• ability to make operating system calls directly
• powerful string operations and regular expressions
• immediate feedback during development

quick and easy:

• variable …